Oddly, insert.xref.page.number and insert.link.page.number are ignored with the 1.72.0 FO stylesheets if linking to a <para>. In some cases this probably makes sense but if page numbering for references is turned off elsewhere then it can look a bit strange.
I suggest one of two enhancements:
(1) Remove the two "or local-name($target) = 'para'" checks from fo/xref.xsl that essentially cause insert.xref.page.number and insert.link.page.number to be ignored.
(2) If option (1) above would cause backward compatibility concerns, then perhaps a new parameter could be added -- something like:
The value of this parameter determines if cross references (xrefs and links) to para in printed output will include page number citations. It has three possible values.
no - No page number references will be generated.
yes - Page number references will be generated for all xref and link elements to para. The style of page reference may be changed if an xrefstyle attribute is used.
maybe - Page number references to a para element will not be generated for an xref or link element unless it has an xrefstyle attribute whose value specifies a page reference.